docs: def acquire_nix(lock_file):  # pragma: no cover
      """Acquire a lock file on linux or osx."""
      fd = os.open(lock_file, OPEN_MODE)
  
      try:
          fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
      except (IOError, OSError):
          os.close(fd)
      else:
          return fd